1. Field of the Invention
The present invention relates to an optical disc which data is written on, read from, and deleted from, and more particularly, to an optical disc having a data wobble in a read-only area for only reading and another wobble, which is different from the data wobble, in a readable/writable area, and having a connection area between the read-only area and the readable/writable area.
2. Description of the Related Art
In general, optical discs, such as DVD-RAMs, DVD-RWs, DVD+RWs, and DVD-Rs, which data is written on, deleted from, and read from, have been used or proposed. In a case of these optical discs, data only for reading (read-only data), e.g., identification and serial number of the optical disc, a version number of a format book, and a writing strategy, is written in an inner portion of the optical disc in a form of unchangeable pits. A readable/writable area where data can be written to, read from and deleted from, follows a read-only area for only reading to which the read-only data regarding the optical disc is written in the form of the pits. Further, a connection zone is formed to be a physical interface between the read-only area and the readable/writable area.
Japanese Patent Publication No. 1993-258469, as shown in FIG. 1, discloses an optical disc having a mirror area 100 formed between an A area 103, which is only readable, and a B area 105, which can be readable and recordable, to maintain constant angular velocity for obtaining regular data density. The mirror area 100 has wobbling pits wp1 and wp2 containing tracking information at a head of each segment SG but does not contain control information such as address.
A DVD-RAM shown in FIG. 2 includes the connection zone between the read-only area and a recordable area in a lead-in area, and the connection zone is formed of the mirror area having no data within a predetermined radius of the optical disc. The mirror area is required to obtain a time margin to master a wobble and header pits with two beams after mastering the pits, which are the read-only data, with one beam during a manufacturing process of the optical disc. The mirror area also provides a drive with information about a starting point of the recordable area following the read-only area.
FIG. 3 is a view of a connection zone applied to a format of a 4.7 GB DVD-RAM. In detail, the connection zone is formed between a read-only data zone for only reading, in which data is written as embossed characters, and a recordable data zone. On the other hand, a DVD+RW, a DVD-RW, or a DVD-R does not have such a connection zone. Instead of the connection zone in the DVD-RAM of FIG. 3, as shown in FIG. 4, a buffer area 115 is formed at a border between a lead-in area 110 and a data area 120 using address information such as a wobble or a land pre-pit (LPP).
As mentioned above, the prior art establishes the connection zone only when the read-only data is written in the form of the pits. However, in a case that the read-only data is written in the form of the pits and the recordable area is written in the form of groups, it is difficult to obtain good-quality groove characteristics due to different manufacturing conditions of the pits and the grooves. Further, in a high-density and high-capacity disc having multi-recording layers, an optical power loss occurs due to dispersion of a write beam when the write beam is illuminated on a pit area. To solve these problems, it is suggested that the read-only data be written in the form of a groove wobble having grooves with wobbles. However, the use of the groove wobble of different specifications, e.g., frequency, amplitude, track pitch, or phase, in both the read-only area and the readable/writable area, may cause errors due to the wobbles of different specification, e.g., a crosstalk of the wobble at an interface between the read-only area and the readable/writable area. Accordingly, the connection zone is required between the read-only area and the readable/writable area when the read-only data is written as the groove wobble, not as the pit.